Grave Secrets of Dinosaurs: Soft Tissues and Hard Science

Summary

Drawing on new breakthroughs and cutting-edge techniques of analysis, Dr. Manning takes us on a thrilling, globe-spanning tour of dinosaur mummy finds—from the first such excavation in 1908 to a baby dinosaur unearthed in 1980, from a dino with a heart in South Dakota to titanosaur embryos in Argentina. And he discusses his own groundbreaking analysis of the recent discovery of a remarkably intact dinosaur mummy in the Badlands of North Dakota. Using state-of-the-art technology to scan and analyse this remarkable discovery, National Geographic and Dr. Manning create an incredibly lifelike portrait. The knowledge to be gained from this exceedingly rare find, and those that came before it, will intrigue dinosaur-loving readers of all ages.

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Grave Secrets of Dinosaurs - Dr. Phil Manning

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INTRODUCTION

LATE IN 1999 A YOUNG PALEONTOLOGIST, Tyler Lyson, was heading home after a day of fossil prospecting on his uncle’s land in the Hell Creek Formation of North Dakota. Water was running low, so it was time to head back home. As Tyler entered a small valley, bounded by a long, low butte on one side and a high domelike butte to the other, he noticed the telltale shapes that indicated a fossil bone.

Tyler had lived in North Dakota his entire life. Much of his childhood had been spent exploring the Badlands that surrounded and underpinned his hometown of Marmarth. From an early age he had shown a keen interest in the fossil remains littering the landscape where he and his brother often hunted for more modern prey. On his trips he was used to meeting a steady stream of academics that also hunted the Badlands—but for an extinct variety of prey. Tyler was a sharp, intelligent young man who was hungry for knowledge and keen to learn. Most children have a period in their life when dinosaurs are a passion, but few can fuel their passion with vast quantities of fossil remains on their doorstep. Many visiting academics recall the incredible fossils that the young hunter had already plucked from the Badlands.

As Tyler crouched down to look at the find, he knew instantly he had found part of a dinosaur tail. This particular tale about a tail has a twist, given that these bones had weathered out of the stone where they had been lodged for more than 65 million years. Such exposure sometimes means there’s more where that came from. A combination of searing summer heat, winter snows, and heavy rain not only sculpted the Badlands, but also has revealed many of the fossils entombed within the sediments.

Gravity is a useful tool for paleontologists in the field. Fossil bones do not roll uphill. So Tyler naturally examined the rock surface immediately above where the exposed tail vertebrae lay. His eye soon spotted the telltale sign of where the vertebrae had fallen from the rock. A patch of bone was still clinging to the rock face, waiting for the next heavy rain storm to reunite it with the bones at the bottom of the slope.

Tyler scrambled up the slope. Just like a layer cake, the sediments of a former floodplain in the Late Cretaceous Period had slowly built up over many years, creating the layers of Hell Creek Formation. As Tyler carefully dug around the tail vertebrae, he saw more buried beneath the surface.

At that sight he hesitated. To start opening a new fossil site at the end of a field season is not a good idea. The problem of someone else discovering the site was not one of Tyler’s worries, since he was out in the back of beyond. His main concern was the coming winter. The heating, freezing, and washing with rainwater takes its toll on fossils that are exposed at the surface. Instead Tyler took out his notebook and GPS receiver to pinpoint the fossil’s position. In the same way a car’s satellite navigation system can nail down where you are on Earth, these systems help us record the positions of paleontological sites so that we can relocate them with ease. Taking GPS coordinates for the site, he noted the location in his field notebook and carefully covered the bones. Tyler then packaged and labeled the bones that had already fallen from the site and brought his hand-sized parcel back to Marmarth. The shape of the bones told Tyler that he had found a dinosaur called a hadrosaur—but how much, he wondered, was buried back where he’d been?

The answer was, incredibly: all of it. For the first time in history a dinosaur with all of its skin, except around a chest wound, would be unearthed. As readers familiar with seeing dinosaurs in museums are aware, the fossil record rarely preserves entire animals. Usually their deaths have left only tough fossil remains of shell, exoskeleton, and bone. From these remains paleontologists are tasked with charting the depths of the history of life on Earth. Yet in rare cases the creatures’ soft tissue has been preserved in stone. Such remarkable fossils enable immense advances in our understanding of long-vanished lives and forgotten worlds.

Dinosaur bones have fascinated human beings for thousands of years. Once upon a time such giant bones were reconstructed into the leviathans of myth and legend. They were not formally classified until the 19th century. Given that reconstructions are based upon the evidence available at a particular point in history, the restorations of dinosaurs have evolved through time. Until the mid-20th century dinosaurs were regarded as failures while we considered ourselves the ultimate expression of the success of life on Earth. The word dinosaur was at that time used to indicate cumbersome, outdated, doomed to fail, or unsuited to environment. Only since the 1970s have dinosaurs been rehabilitated, regaining their power to awe a popular audience.

Since the naming of the Hell Creek Formation 100 years ago, the fossil remains from the desolate Badlands have inspired generations of paleontologists to hunt for the elusive treasures of past life. These vast deposits contain some of the last fauna and flora from the age of the dinosaurs. Like many paleontologists before me, I, too, have been drawn to this fertile ground of T. rex and its kin. Five years would pass before Tyler returned to the hadrosaur site. Only then did he realize the unique potential of this fossil. This is when our paths first crossed and when we started on our exciting journey of discovery.

I am currently employed as a lecturer in paleontology in the School of Earth, Atmospheric, and Environmental Sciences at the University of Manchester in England and also as a Research Fellow at the Manchester Museum. For more than 20 years I have had the good fortune to concentrate much of my efforts on dinosaurs. The fossilized bones of the hadrosaur that Tyler had discovered would allow the resurrection of many grave secrets locked in stone for more than 65 million years. The presence of rare soft-tissue structures would ensure that this fossil would become a member of a prehistoric elite—dinosaur mummies.

Since I started working at the University of Manchester I have been lucky enough to explore the diverse disciplines that have begun to interface with the science of paleontology. While the days of shovel and spade have not left the field, many 21st-century methods and techniques are becoming available. The excavation process is now treated more like a crime scene, with the macabre secrets of death waiting to be unearthed, analyzed, and interpreted. While we are not greeted with the stench of rotting flesh, cutting-edge science carefully processes the many clues to unlock ancient worlds and the animals that once occupied them.

Every care would be taken to remove, record, and scrutinize the sedimentary blanket that had wrapped Tyler’s mummy in a protective cocoon for more than 65 million years. The chemical signatures of environmental change, decay, and mineralization would be painstakingly logged, collected, and shipped back to Manchester for analysis. The samples would be located within a vast three-dimensional digital outcrop map, acquired using the latest laser-scanning technology, helping to place the fossil spatially in both time and changing environment. As the dinosaur fossil was slowly prepared using more traditional paleontological techniques, samples were carefully taken from the delicate skin envelope in the hope that fragile structural biomolecules (proteins and their breakdown products) locked in the mineral-rich skin envelope had survived. X-ray computerized-axial tomography would be used to look into the innermost secrets of our dinosaur, using techniques more commonly applied to the space program. State-of-the-art computer simulations would also be applied to our dinosaur to reveal much of how the animal once walked and ran across the Hell Creek floodplain.

Since the first mummified dinosaur was found 100 years ago, paleontological science now has the potential to transport us back to the final moments of a hadrosaur in the twilight years of the reign of the dinosaurs.

CHAPTER ONE

DEATH OF A DINOSAUR

"One hundred percent of us die,

and the percentage cannot be increased."

—C. S. Lewis

OMINOUS STORM CLOUDS built over the shores of the coastal floodplain behind them. Sweltering moisture-laden air blew through the endless march of dinosaurs. It made the elder members of the herd uneasy, increasing the urgency of the herd’s pace. The floodplain had the potential to become treacherous if the rains came early.

The vast herd of hadrosaurs had trodden the same trails for millennia, leaving millions of tracks along the paths of migration. Each step brought them closer to the relative safety of the higher plateau and added security of numbers at the breeding grounds. The Tyrannosaurus rex that were continually shadowing the herd had already picked off numerous stragglers over the past few weeks. The herd was vulnerable out in the open, but their sheer numbers worked in their favor. They outnumbered the predators two hundred to one, an intimidating prospect even for the boldest predator. Natural selection was ensuring that only the fittest animals would make it through to the breeding grounds. The hadrosaurs tried hard to remain a tight herd, operating as a cooperative deterrent. However, a severe storm on the plain could cause the lowland rivers to swell. The entire herd could be wiped out by a flood.

While adult hadrosaurs waded through the many water-courses that crisscrossed the vast floodplain with ease, younger animals struggled with the currents and the thrashing bodies of larger, stronger members of the herd. As they crossed each stream, a cautious watch was kept for the crocodiles that lay in wait, still beneath the waters of major crossing points. The crocodiles ate their fill twice a year from the migration of the great herds. While T. rex relied upon speed and sheer power, the crocodiles were the ultimate stealth predators, ready to explode from the waters and drag their prey to a watery grave.

The herd reached the main river course, which each year offered a subtly different challenge due to its meandering path through the plain. The herd began to back up on the banks of the wide river. The mist rising over the steady current of the dark, silt-laden waters concealed its immense energy.

A deep, powerful tone resonated from the lead animals. A crossing site had been selected. The first animal, a large dominant male, stepped over the shallow precipice separating the floodplain and freshly deposited sands banked up against the inside meander of the river. The lead male did not sink into the sand, but assertively padded toward the water’s edge. He faltered slightly as he reached the edge, knowing his actions would determine the fate of the whole herd. Nostrils flared and bellowing loudly, the 8,000-pound male propelled himself into the water, pushing up a vast bow wave before his broad chest. Soon only his back, neck, and head were visible above the dark waters, as his powerful legs pushed off the soft sediments of the riverbed. His direction of travel was a gentle diagonal traverse of the river, carried by the downstream flow. A steady line of herd members advanced to the edge of the river. The last major hurdle of the season’s migration would soon be behind them.

After several hundred of the herd had entered the river course, an explosion of water and teeth erupted as a huge crocodile launched itself from the shallows. A young hadrosaur’s head was grasped in the vice-like grip of the crocodile’s jaws. A second explosion followed as another crocodile clamped its jaws around a leg. Screams of alarm echoing along the shore, the herd retreated from the splashing frenzy of jaws, flesh, and bloodstained waters. In a few seconds the young hadrosaur had disappeared from sight. A quiet cloak of death hung over the water. Yet instinct to reach the breeding grounds overcame fear. The crossing resumed.

By midday all but a few stragglers were waiting to take their turn on the now trampled sediments of the river crossing. The crocodiles had feasted frequently for most of the morning, taking dozens of animals, but the numbers of prey left the predators sated and torpid. A young male, not more than ten years old, nervously padded his way to the water’s edge. The sweet smell of the water was now tainted with the acrid taste of blood and feces.

As the young male began the crossing, he could already see large numbers of the herd on the opposite bank cloaked in a vast cloud of steam rising from their drying bodies in the midday sun. Plunging in, the animal soon found the river dragging him farther downsteam than was safe. Soon the banks of the river would be too steep for the animal to escape the undertow of the current. Suddenly aware of his plight, the young male began to fight back against the quiet but relentless current. What had started as a tranquil crossing transformed into a struggle for survival. As he pushed desperately with his powerful leg and tail muscles, alarm calls from the opposite banks of the river rose as the herd called to the rapidly disappearing male. As the male was dragged into the vast wasteland of waters where tributaries swelled the river further, the herd disappeared from his view. The exhausted male began to give in to fatigue. The first inhaled water filled the lungs of the hapless animal. In another few minutes the hadrosaur slowly drifted, motionless in the waves.

Another wide meander of the river was dotted with sandbars, a function of the slower moving waters in the inner bend of the watercourse. The fresh carcass of the male hadrosaur settled partially submerged in the waterlogged sands. A small solitary crocodile, a Borealosuchus, attempted to gain entry through the tough hide of the animal. The croc, too, would eat his last fill that day. The rains began to fall. The division between river and sky soon merged as the deluge increased. The river slowly rose over the remains of the hadrosaur, rapidly cocooning the animal in a suit of soft, fresh sediment.

Reconstructing a scene that occurred more than 65 million years ago might initially seem far-fetched, but locked within any landscape and its fossils are clues that can help resurrect such places and events. The toolkit that helps unearth these events is similar to that of a crime-scene investigator, albeit the scene of the crime is far from fresh.

The processes that affect a body after death are possibly the most difficult secrets to exhume. Within minutes of an organism’s demise, the body begins to decompose. The complex relationship between body chemistry and the environment in which it decomposes is one we will explore, as well as the processes of decay. Deciphering the grave secrets of a dinosaur is no easy task, given that millions of years have laid waste to the evidence. Where once a living, breathing organism roamed the land are now only rare, disjointed fossil remains locked in stone. To resurrect a dinosaur from its rocky tomb requires skills that have steadily expanded the science of paleontology.

Eight years ago a prehistoric crime scene was uncovered by a young fossil hunter, Tyler Lyson, that would lead dozens of scientists from many disciplines to start the painstaking process of reconstructing the last steps, burial, and fossilization of a dinosaur in the Hell Creek Formation of North Dakota. The dinosaur, which has been nicknamed Dakota, is one of a rare type of fossil often called dinosaur mummies. As used by paleontologists, this loosely applied term has quite a different meaning than that used by archaeologists, yet such fossils provide unique information that has allowed us to fill in many gaps in our knowledge about dinosaurs. This new find represents an exciting step forward in a long legacy of discovery.

Before I focus on this specific find, it is worth a quick review of what constitutes a dinosaur. Many children have come across this famous extinct group in books, on TV, and in the movies. Dinosaurs are a British invention, although the fossil remains of antediluvian beasts were known for centuries, from every continent across the globe. The Chinese have long spoken of Lung, the dragon, whose bones were scattered across many provinces of China and were often rendered into an apothecary’s jar for medicinal use. Such tales were most likely based upon giant fossil bones, sometimes from dinosaurs.

The ancient Greeks and Romans also recorded fossil hunting and the interpretation of their finds. A Roman statesman and general, Quintus Sertorius, in 81 B.C. was reported to have found an 80-foot-long skeleton in North Africa. Pliny the Elder, a first-century Roman scholar famous for his book Naturalis Historia, documented the discovery of a 69-foot-long giant revealed by an earthquake, and also described at length the life and habits of the mythical griffins of Mongolia. The area of Mongolia that gave rise to this myth is well-populated by the fossil remains of the lion-sized, beak-faced dinosaur Protoceratops. In the third century A.D., the Roman historian Julius Solinus tells of an occasion in the first century B.C. when retreating floodwaters exposed a skeleton nearly 50 feet long in the collapsed sediments of a riverbank.

The Renaissance signified an important step forward in paleontological understanding. Leonardo Da Vinci made many notes on fossil mollusk shells from high mountain passes, speculating as to their origin and preservation. In the year 1565 Conrad Gesner published On Fossil Objects, which was one of the earliest attempts to improve on the work of classical scholars. The book was beautifully illustrated with woodcut prints of fossil specimens, a great advance on the often obscure written descriptions.

Some descriptions in Britain from the 17th and 18th centuries carry wonderfully inappropriate names, such as Scrotum humanum. Rev. Robert Plot first described the fossil in question as a human thigh bone in 1676, but the creature was not named S. humanum till 1763 by Robert Brookes. Fortunately, the one with this particular distal end of a thigh bone (femur) now goes by its more recent name, Megalosaurus. A number of saurian fossils were excavated and named in the early part of the 19th century, such as Megalosaurus (1824), Iguanodon (1825), and Hylaeosaurus (1832), and many more followed. What became increasingly clear to those who studied these bones was that they were an extinct group of animals, unlike anything alive today. What was needed was a suitable means by which to classify these animals.

Richard Owen, a brilliant comparative anatomist, was granted funds by the British Association for the Advancement of Science to explore these fossil remains of antediluvian beasts. At the 1841 meeting of the Association in Plymouth, Owen presented many of his findings, and these were published in 1842, when he first used the name dinosauria to unite this distinct tribe of animals. Dinosaurs had been officially invented. Owen stated that dinosaurs were a distinct tribe of saurian reptiles, deserving a collective name, dinosauria, literally meaning terrible lizard. He defined dinosaurs by the possession of five fused sacral vertebrae, the region of the backbone that runs through the hip (pelvic) region. This definition has been somewhat refined and expanded in recent years, now including such characteristics as the possession of a rear-facing shoulder joint and an open hip socket among some specimens.

Dinosaurs were first released on the public, so to speak, in 1854 in the grounds of the Crystal Palace at Sydenham. The palace, a vast iron-framed glass house, had been moved from its site in Hyde Park, where it had formed the centerpiece of the Great Exhibition of the Works of Industry of All Nations, the first world’s fair. A decision was made to populate the grounds of Sydenham Park with life-size models of dinosaurs, marine reptiles, crocodiles, and pterosaurs. The sculptor, Benjamin Waterhouse Hawkins, was commissioned to resurrect this menagerie for the delectation of the public! Dinosaurs were an instant hit, and thousands flocked to see the vast prehistoric reconstructions. Dinosaurs were immortalized by Charles Dickens in the opening passages of Bleak House: Implacable November weather. As much mud in the streets as if the waters had newly retired from the face of the earth, and it would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling like an elephantine lizard up Holborn Hill.

The public obsession with dinosaurs has not waned in more than 150 years. The study of the fossil remains of dinosaurs has expanded into a vast field of research on every continent. From humble, albeit sensational, beginnings in the 19th century to the 21st century with its a vast array of methods and tools, scientists continue to unlock the grave secrets of dinosaurs.

The dinosaurs were subdivided into two distinct groups (orders) by Harry Seeley in 1888. The division was based upon the geometry of their pelvic girdles: the saurischia (lizard-hipped) and ornithischia (bird-hipped). This major division in this group occurred right at the beginning of the Age of Dinosaurs, sometime in the Triassic Period. Some have argued, based on the variation between saurischian and ornithischian dinosaurs, that each has its own distinct ancestor. However, most now agree that these two major dinosaurian orders belong in a single natural group (superorder), the dinosauria. The molecular tools available to biologists to study the evolutionary relationships of modern species are not easily applied to the fossil record, meaning such extinct family trees (phylogenies) are based upon skeletal remains and morphology. Ideally, we would obtain genetic sequences from soft tissues that would allow the reconstruction of molecular phylogenies.

While on the subject of evolutionary classification, it’s worth explaining how and why we name all living creatures. Starting with the familiar, paleontologists have a habit of giving a dinosaur a nickname when excavating it. For instance, the T. rex Sue and Stan were named after their respective finders; our dinosaur’s name was chosen by Tyler, based simply on its geographical provenance. More formally, all types of birds, mammals (including ourselves), fish, amphibians, reptiles, crustaceans, and bacteria have at least two names that follow internationally accepted codes for naming plants and animals. These are the International Code for Zoological Nomenclature (ICZN) and the International Code for Botanical Nomenclature (ICBN). Within these two volumes are the rules of naming a new species. A new name is given only when a plant or animal is discovered for the first time and is shown to be distinct from any known species. The animal—its morphology, fossil, and/or structure—is then formally described and published within a peer-reviewed journal. A new species is then presented to the scientific world, and often to the wider world via the media.

The classification of specific plants and animals into distinct groups or tribes is also worth a quick review. The binomial system applied to naming plants and animals was devised by Carolus Linnaeus in his important work Systema Naturae, published in 1735. Linnaeus subdivided a name into first the genus and then species names—for example, we are Homo sapiens (always written in italics). The Linnaean system allowed species to be classified within a hierarchical structure, starting with kingdoms. Kingdoms are divided into classes, then orders, which are further divided into genera and eventually into species. The classification is based upon observable characteristics, meaning that many early classifications resulted in very strange family trees. The more specimens and types of characteristics you have, usually the more robust the family tree. However, a new find that possesses a distinct character—say, a theropod dinosaur with feathers—can have an enormous impact that results in major revisions of evolutionary relationships. So, if we were to look at the classification of the species Edmontosaurus annectens, it would look like this:

Kingdom Animalia

Phylum Chordata

Class Sauropsida

Subclass Diapsida

Infraclass Archosauromorpha

Superorder Dinosauria

Order Ornithischia

Suborder Cerapoda

Infraorder Ornithopoda

Family Hadrosauridae

Subfamily Hadrosaurinae

Genus Edmontosaurus

Species annectens

Our own evolutionary path parted with the ancestors of dinosaurs sometime in the Carboniferous Period, when the diapsids (reptiles, and later to include birds) and synapsids (to become mammals) split company. However, the basic tetrapod (four-feet) skeletal plan is still recognizable, shared by all vertebrates. I love taking my undergraduate class to the Manchester Museum, across the road from the department in which I teach. I show students the five fingers in the hand, the vestigial hips, and the seven neck vertebrae of a sperm whale (Physeter microcephalus), and compare those with elephants (Loxodonta), antelopes (Antilope), and chimpanzees (Pan troglodytes). The rough skeletal blueprint is often separated only by form. The evolutionary distance between animals is beautifully displayed by their adaptations, a function of the selective environmental pressures that have dictated their survival.

Occasionally a name is given to an animal that has already been formally described, but has been missed or misidentified by the author. When this occurs, the first name has priority over the second. In some cases this has meant some splendid names have bitten the dust. Brontosaurus (thunder-lizard) was named by Othniel Marsh in 1879, after the remains of Apatosaurus (deceptive-lizard) had already been formally described by Marsh in 1877. The fossil bones were from the same species, so the wonderfully apt name of Brontosaurus had to be dropped. The size difference between the two different fossils misled Marsh into thinking he had a new type of dinosaur, when in fact the animals were only at different stages of growth. The misidentification was not recognized until 1903, allowing the term Brontosaurus to be well and truly fixed in scientific and popular literature.

The fossil find made by Tyler in the Badlands of North Dakota seemed to be a member of a group of dinosaurs called the hadrosaurs. These are ornithischian dinosaurs; although the unfortunate name refers to the pelvic bones resembling those of modern birds, they are not related. It is the other half of the dinosaur family tree, the saurischians, that are the direct ancestors of modern birds. Saurischian dinosaurs include T. rex, Allosaurus, Velociraptor—in fact, all predatory dinosaurs—and also the vast sauropod dinosaurs, including Diplodocus and Apatosaurus.

The family Hadrosauridae, sometimes called duck-billed dinosaurs, was named in 1869 by Edward Drinker Cope. The fossil remains of this group are found in Upper Cretaceous rocks of Asia, Europe, and North America. The hadrosaurs are further subdivided into the subfamilies Lambeosaurinae and Hadrosaurinae, because only the former had crests on their heads. Hadrosaur fossils were the first skeletal dinosaur remains to be discovered in North America, in 1855, although the tracks of dinosaurs had been known since the early half of the 19th century. Many fossil teeth and partial skeletons of hadrosaurs were discovered over ensuing years.

Several species of hadrosaurs have been found in the Hell Creek Formation: the more common Edmontosaurus, the rare and very large Anatotitan, and some possible crested lambeosaurine (literally hollow-crested) hadrosaurs that have not been formally described yet. Tyler was pretty sure that his new dinosaur find was an Edmontosaurus. Yet that species breaks down into three subspecies: Edmontosaurus regalis, Edmontosaurus annectens, and Edmontosaurus saskatchewanensis. Only a full excavation would reveal the exact species of dinosaur that Tyler had found.

The name Edmontosaurus was first given to a dinosaur in 1917, based upon some fossil remains found near Edmonton, Canada (the name means Edmonton lizard). The first remains of this dinosaur were named Edmontosaurus regalis by the Canadian paleontologist Lawrence Morris Lambe in 1917.

Edmontosaurus was a plant-eating (herbivore) dinosaur that is often reconstructed as a biped, walking on two legs, but it almost certainly used its forearms to occasionally walk on all fours as a quadruped. The arms were relatively short compared to the legs, and more lightly built. The restoration of this dinosaur’s hands and feet often indicate that it possessed rounded hooves and soft fleshy pads to support the animal’s weight. The fossil bone cores that once terminated each toe are broad and flat, indicating that